Quasi-Vortex Electromagnetic Wave Radar Forward Looking based on Echo Phase Weighting

SHU Gaofeng; WEI Yixin; LI Ning

doi:10.11999/JEIT250542

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SHU Gaofeng, WEI Yixin, LI Ning. Quasi-Vortex Electromagnetic Wave Radar Forward Looking based on Echo Phase Weighting[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250542

Citation:

SHU Gaofeng, WEI Yixin, LI Ning. Quasi-Vortex Electromagnetic Wave Radar Forward Looking based on Echo Phase Weighting[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250542

SHU Gaofeng, WEI Yixin, LI Ning. Quasi-Vortex Electromagnetic Wave Radar Forward Looking based on Echo Phase Weighting[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250542

Citation:

SHU Gaofeng, WEI Yixin, LI Ning. Quasi-Vortex Electromagnetic Wave Radar Forward Looking based on Echo Phase Weighting[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250542

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Quasi-Vortex Electromagnetic Wave Radar Forward Looking based on Echo Phase Weighting

doi: 10.11999/JEIT250542 cstr: 32379.14.JEIT250542

1.
School of Computer and Information Engineering, Henan University, Kaifeng 475004, China
2.
Henan Key Laboratory of Big Data Analysis and Processing, Henan University, Kaifeng 475004, China
3.
Henan Engineering Research Center of Spatial Information Processing, Henan University, Kaifeng 475004, China

Funds: The Natural Science Foundation of Henan (242300421170)

Received Date: 2025-06-04
Rev Recd Date: 2025-09-17

Available Online: 2025-09-23

Abstract

Abstract

Objective Forward-looking radar imaging plays a critical role in multiple applications. Numerous algorithms have been proposed to enhance azimuth resolution; however, improvement remains difficult due to the limitations imposed by antenna aperture. Existing high-resolution techniques, including synthetic aperture radar and Doppler beam sharpening, rely on Doppler bandwidth and inevitably create blind spots in the forward-looking region. Vortex electromagnetic waves carrying orbital angular momentum offer potential in forward-looking scenarios because of the orthogonality between different orbital angular momentum modes. In conventional vortex electromagnetic wave imaging, a Uniform Circular Array (UCA) is used to generate and transmit multi-mode vortex electromagnetic waves. Yet, the UCA-generated waves suffer from main lobe divergence, which disperses energy and weakens echo signals, while multi-mode transmission increases system complexity. To address these issues, this paper proposes a Quasi-Circular Array (QCA) that reduces system complexity, produces vortex electromagnetic waves with more concentrated main lobes, and preserves phase linearity. In addition, a post-processing method based on echo phase weighting is introduced. By applying phase modulation to the single-mode echo received by each antenna element, a complete equivalent multi-mode echo is synthesized. The proposed method enhances azimuth resolution and exhibits strong anti-noise performance. Methods To obtain clear images under low Signal-to-Noise Ratio (SNR) conditions, a phase modulation echo post-processing method combined with a QCA is proposed. The QCA first generates a single-mode vortex electromagnetic wave to illuminate the region of interest. Each element of the array then receives and stores the echo. Phase modulation is subsequently applied to the stored echo to generate signals of specific modes, thereby synthesizing an equivalent multi-mode echo with enhanced amplitude that preserves target information. This approach demonstrates strong potential for practical applications in forward-looking radar imaging under low SNR conditions. Results and Discussions When noise is added to the echo and imaging is performed (Figure 11), the proposed method achieves superior results under noisy conditions. As noise intensity increases, a clear target can still be reconstructed at a SNR of –10 dB. Even when the SNR is reduced to –15 dB and the target is submerged in noise, the contour features of the reconstructed target remain distinguishable. These results demonstrate that the method has strong anti-noise performance. In addition, when imaging is performed within a smaller mode range, the azimuth resolution achieved by the proposed method improves by an average factor of 2.2 compared with the traditional method (Figure 9). The improvements in resolution and anti-noise performance can be attributed to two factors: (1) The vortex electromagnetic waves generated by the QCA experience reduced destructive interference due to the asymmetric spatial distribution of array elements, producing waves with more concentrated main lobes, lower side lobes, and higher radiation gain. (2) Applying phase modulation in echo processing reduces the pulse repetition frequency of the vortex electromagnetic wave at the transmitting end, thereby lowering system complexity. Conclusions This study proposes a method capable of effective imaging under low SNR conditions. The echo expression of the electric field generated by the QCA is derived, and the radiation gain and phase characteristics of the quasi-vortex electromagnetic wave are analyzed. In addition, an echo post-processing method based on phase modulation is introduced. Simulation results demonstrate that, compared with the traditional UCA method, the proposed approach generates vortex electromagnetic waves with more concentrated main lobes, lower side lobes, and higher gain, while improving azimuth resolution by a factor of 2.2. Even at a SNR of –15 dB, the reconstructed imaging results remain distinguishable.
- Vortex electromagnetic waves,
- Forward-looking radar,
- Quasi-circular array,
- Echo phase weighting

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References(26)

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